Automotive alternator slip ring assembly

Abstract

A slip ring assembly (36) adapted to mount on a rotor shaft (38) and to sealingly mount between respective seal surfaces (136,70) on a mold (134) and on a pole piece (24) during molding of a molded rotor assembly (20) is disclosed. The slip ring assembly (36) has a hub (94) supporting a pair of slip rings (102,104), a pair of terminals (96,98) and a mold shutoff ring (100) connected to the terminals (96,98). Seal surfaces (118,120) on the mold shutoff ring are adapted to sealingly mate with the respective seal surfaces on the pole piece (24) and on the mold (134) and to withstand large compressive loads being applied across the mold shutoff ring (100). The mold shutoff ring (100) prevents molten mold material from passing from the mold (134) to the slip rings (102,104) during molding of the molded rotor assembly (20).

I claim: 
     
       1. A slip ring assembly for use in an attachment arrangement for sealingly mounting the slip ring assembly between a mold and a pole piece, each of the mold and pole piece having a seal surface, and around a rotor shaft of a rotor assembly during injection molding of a mold material under pressure, the slip ring assembly comprising: at least one slip ring;   at least one electrically conductive terminal connected to the slip ring; and   a mold shutoff ring supporting the terminal and having seal surfaces, the seal surfaces of the shutoff ring being adapted to sealingly mate with the respective seal surfaces on the mold and on the pole piece and sufficiently strong to withstand pressures applied to the mold shutoff ring during injection molding;   whereby when the mold shutoff ring mates with the pole piece and the mold during a molding operation, the pressurized molten mold material is prevented from passing between the shutoff ring and the mold and between the shutoff ring and the pole piece.   
     
     
       2. The slip ring assembly of claim 1 wherein: the seal surfaces of the mold shutoff ring include an axial inboard seal surface and an axial outboard seal surface, the axial inboard and outboard surfaces being axially spaced apart with the inboard seal surface being adapted to mate with the seal surface of the pole piece and the outboard seal surface being adapted to mate with the seal surface of the mold during the molding operation. 
     
     
       3. The slip ring assembly of claim 2 wherein: the mold shutoff ring includes an outer radial seal surface adapted to mate with the seal surface of the mold during the molding operation.   
     
     
       4. The slip ring assembly of claim 1 wherein: the shutoff ring has a radially inner surface which is sized and configured to mount on the rotor shaft whereby when the slip ring assembly is mounted on the rotor shaft, the rotor shaft provides radial support to the shutoff ring.   
     
     
       5. The slip ring assembly of claim 1 wherein: at least one of the seal surfaces of the mold shutoff ring is planar. 
     
     
       6. The slip ring assembly of claim 1 wherein: the shutoff ring is annular.   
     
     
       7. A molded rotor assembly comprising: an elongate rotor shaft extending along a longitudinal axis;   a pair of annular pole pieces axially aligned along and mounted on the rotor shaft with a region being defined between the pole pieces;   a coil wire held within the region and having a plurality of turns and a pair of free ends;   a slip ring assembly including a pair of slip rings; a pair of terminals and a mold shut off ring having an inboard axial surface in sealing engagement with one of the pole pieces and an outer peripheral surface, the terminals connected to and extending between respective slip rings and free ends of the coil wire; and   mold material molded to and securing together the outer peripheral surface of the mold shut off ring and the one of the pole pieces;   wherein the sealing engagement between the mold shut off ring and the one of the pole piece prevents mold material from passing between the mold shut off ring and the pole piece.